Study on failure envelopes of bucket foundations for offshore wind turbines after local scour

Based on the finite element software, the formation of local scour hole was simulated by model change function. Swipe and probe method were combined to study the bearing capacity of bucket foundation under the combined loading of vertical load V, horizontal load H and bending moment M after local scour. The results show that both the horizontal ultimate bearing capacity and bending moment ultimate bearing capacity are both weakened deeply by local scour. Under the combined loading of V-H and V-M, horizontal and bending moment ultimate bearing capacity of bucket foundation can be increased by appropriate increasing vertical load V. The failure envelope lines of V-H and V-M after local scour have similar curve shapes, furthermore, a mathematical expression is proposed to approximate the failure envelopes of V-H and V-M. The H-M failure envelope lines of bucket foundation in the first quadrant shows a monotonically decreasing trend, which is obviously affected by local scour. With increasement of scour depth, the bearing capacity of bucket foundation decreases in a parabolic trend. Through monotonic and two-dimensional combined loading, the bearing capacity change of bucket foundation after local scour is clarified. Finally, the V-H-M three-dimensional failure enveloping surface under Sd=0.2D is drawn, which plays a reference role for the bearing condition of bucket foundations in actual engineering after local scour action. © 2022, Solar Energy Periodical Office Co., Ltd. All right reserved.